The α,β-unsaturated aldehyde compounds are useful compounds as perfumes, intermediates for perfumes, or raw materials for medicines or agricultural chemicals.
Examples of the α,β-unsaturated aldehyde compounds usable as perfumes include trans-2-hexenal, trans-2-heptenal, trans-2-octenal, trans-2-nonenal, trans-2-decenal, trans-2-undecenal, trans-2-dodecenal, trans-2-tridecenal, 2,4-octadienal, 2,4-nonadienal, 2,6-nonadienal, 2,4-decadienal, 2,4-undecadienal, 2,4-dodecadienal, citral, α-methylenecitronellal (“Bergamal”), cinnamaldehyde (cinnamic aldehyde), α-methyl cinnamaldehyde and α-hexyl cinnamaldehyde.
Also, examples of the α,β-unsaturated aldehyde compounds usable as the intermediates for perfumes include derivatives of campholenic aldehyde which are usable as a raw material for perfumes such as “Sandalmysole core”, “Bacdanol” and “Sandalore”, derivatives of p-isobutyl benzaldehyde which are usable as a raw material for perfumes such as “Suzaral”, and derivatives of p-t-butyl benzaldehyde which are usable as a raw material for perfumes such as “Lilial”.
These α,β-unsaturated aldehyde compounds may be produced by various methods. As one of these methods, there is known the method of subjecting a raw aldehyde compound to an intermolecular condensation reaction. In such a method of producing the α,β-unsaturated aldehyde compound by the intermolecular condensation reaction of the raw aldehyde compound, when two different kinds of aldehyde compounds are subjected to cross aldol condensation in the presence of a known aldol condensation catalyst such as sodium hydroxide, the respective aldehyde compounds individually undergo a condensation reaction of same kinds of aldehyde compounds, so that a selectivity of the aimed α,β-unsaturated aldehyde compound by the cross condensation reaction tends to be lowered and, therefore, the purification of the resultant product tends to inevitably become complicated.
There has been described, for example, the method of producing the α,β-unsaturated aldehyde compound by subjecting (A) an aldehyde compound containing a larger number of carbon atoms and (B) an aldehyde compound containing a smaller number of carbon atoms to a cross condensation in an inert solvent in the presence of an organic acid ammonium salt (for example, refer to JP 2004-513871A).
However, the above conventional method has problems such as a relatively large molar ratio of the aldehyde compound (B) to the aldehyde compound (A) (aldehyde compound (B)/aldehyde compound (A)) ranging from 2.5 to 10, necessity of conducting the condensation reaction in a non-polar solvent capable of forming an azeotropic mixture with water, and unsatisfactory yield of the aimed product. Further, in the above method, as the organic acid ammonium salt catalyst, it is required to use an ammonium salt of a lower organic acid having 1 to 3 carbon atoms such as piperidinyl acetate, pyrrolidinium acetate, ammonium acetate, dimethyl ammonium pyridinyl acetate, morpholine acetate, piperidinyl formate and piperidinyl propionate. In Examples of JP 9-216847A, there is disclosed the method for producing an α-alkyl cinnamaldehyde by using acetic acid as a protonic acid and pyrrolidine as an amine.